Blocked isocyanates have been employed in coating applications wherein the blocked isocyanates and a polyhydroxyl-containing compound are formulated together to form one package coatings. Upon heating, the blocked isocyanate deblocks thereby forming --NCO groups which can then react with an --OH group or any other group reactive with an isocyanate group such as primary or secondary amine groups.
Catalysts are often employed to facilitate the deblocking reaction. Wicks, Jr. in "Blocked Isocyanates", PROGRESS IN ORGANIC COATINGS, 3 (1975), pp 73-99, discloses such suitable deblocking catalysts as tertiary amines, ammonium compounds, organometal compounds and metal halides of such metals as tin, zinc, bismuth, titanium, magnesium, calcium, strontium or barium.
The present invention concerns a new group of catalysts, organo phosphorus compounds, for deblocking blocked isocyanates.
In some instances, these phosphorus-containing catalysts result in deblocking the blocked isocyanate at a lower temperature or in less time at a comparable temperature.